Sarcocystis

Sarcocystis

[sahr″ko-sis´tis]

a genus of coccidian protozoa parasitic in birds, reptiles, and mammals, including humans, cattle, horses, sheep, swine, and rabbits and other rodents, occurring as elongated cylindrical bodies (sarcocysts) in the host's muscles. They have an obligatory two-host life cycle, involving sexual reproduction in the definitive host (a carnivore) and asexual reproduction, including schizogony and sarcocyst formation, which occurs in the intermediate host. Infection is transmitted by ingestion of the sporocysts in the feces passed by infected animals. See also sarcocystosis.

Sarcocystis boviho´minis a species for which cattle are the specific intermediate hosts and humans the definitive hosts; it causes intestinal sarcocystosis in humans. It was formerly considered to be combined with S. suihominis in a single species, S. hominis (Isospora hominis).

Sarcocystis lindeman´ni a species causing human infection, most cases of which are asymptomatic, although it may cause polymyositis sometimes associated with eosinophilia.

Sarcocystis suiho´minis a species for which swine are the specific intermediate hosts and humans the definitive hosts; it causes intestinal sarcocystosis in humans. It was formerly considered to form a single species with S. bovihominis, called S. hominis (Isospora hominis).

Sarcocystis

(sar'kō-sis'tis),

A genus of protozoan parasites, related to the sporozoan genera Eimeria, Isospora, and Toxoplasma, and placed in a distinct family, Sarcocystidae, but with the above genera in the same suborder, Eimeriina, within the subclass Coccidia, class Sporozoea, and phylum Apicomplexa. Tissue stages of Sarcocystis are usually seen as thick-walled cylindric or (often extremely large [1 cm or more]) fusiform cysts (Miescher tubes) in reptile, bird, or mammal striated muscles. Cysts are smooth in the house mouse form or with radial spines (cytophaneres) in sheep or rabbit; contents may be compartmentalized by septa. Variably shaped spores (Rainey corpuscles) probably are peripheral rounded cells (sporoblasts, cytomeres) that divide to form mature "spores" (bradyzoites), motile bodies when released from the cyst; sexual stages have been described in tissue cultures. These parasites are abundant but rarely of pathogenic significance. Humans who have ingested meat containing the mature sarcocysts serve as the definitive hosts; fever, severe diarrhea, abdominal pain, and weight loss have been reported in a small number of immunocompromised hosts. When humans accidentally ingest oocysts from other animal stool sources, the sarcocysts that develop in human muscle appear to cause no inflammatory response.

[sarco- + G. kystis, bladder]

Sarcocystis

/Sar·co·cys·tis/ (sahr″ko-sis´tis) a genus of parasitic protozoa that occur as sporocysts in the muscle tissue of mammals, birds, and reptiles.

Sarcocystis

a genus of parasitic protozoa in the family Sarcocystidae. The definitive hosts are domestic and wild carnivores in which they appear as a form of coccidiosis. Birds and reptiles are also infected (depending on the species). It appears to be part of any prey-predator system, e.g. snake, rat, owl, mice, etc. The effects of their intermediate stages are manifested as the disease sarcocystosis.

Sarcocystis arieticanis

has a dog-sheep cycle.

Sarcocystis bertrami (syn. Sarcocystis equicanis)

has a dog-horse cycle and produces cysts in muscles but without clinical disease.

Sarcocystis bovifelis

see S. hirsuta (below).

Sarcocystis capracanis

has a dog (coyote, fox)-goat cycle; not pathogenic.

Sarcocystis cervi

cysts found in deer.

Sarcocystis cruzi (syn. Sarcocystis bovicanis)

has a dog (and other feral canids)-cattle cycle; causes fever, anorexia, anemia and weight loss in cattle but the microscopic cysts found in dogs are not pathogenic. See also sarcocystosis.

Sarcocystis cuniculi

cysts found in wild and domesticated rabbits but without apparent pathogenicity in rabbits. It has a cat-rabbit cycle and the macroscopic cysts in cats are pathogenic.

Sarcocystis equicanis

see S. bertrami (above).

Sarcocystis fayeri

has a dog-horse cycle but appears not to be pathogenic to the horse.

Sarcocystis fusiformis

has a cat-buffalo cycle but appears not to be pathogenic in the water buffalo.

Sarcocystis gigantea (syn. Sarcocystis ovifelis)

has a cat-sheep cycle; the cysts in sheep are very large and visible with the naked eye but are not pathogenic.

Sarcocystis hemionilatrantis

has dog or coyote-mule deer cycle and the disease in young deer may be fatal.

Sarcocystis hericanis

has a dog-goat cycle.

Sarcocystis hirsuta (syn. Sarcocystis bovifelis)

has a cat-cattle cycle and is not pathogenic in cattle.

Sarcocystis hominis (syn. Sarcocystis bovihominis)

has a human-cattle cycle, the enteric infection in humans causing diarrhea, and the cysts in the muscles of cattle having no observable effect.

Sarcocystis kortei

the definitive host is unknown, the intermediate host is the rhesus monkey but the cysts in its muscles appear to cause no disability.

Sarcocystis levinei

has a dog-buffalo cycle but causes no illness.

Sarcocystis lindemanni

humans are the intermediate host but the final host is unknown.

Sarcocystis medusiformis

has a cat-sheep cycle.

Sarcocystis miescheriana (syn. Sarcocystis suicanis)

has a dog (raccoon, wolf)-pig cycle but no known pathogenicity.

Sarcocystis moulei

has a cat-goat cycle.

Sarcocystis muris

has a cat-mouse, rat, vole, etc., cycle but the cysts are not pathogenic.

Sarcocystis nesbitti

rhesus monkeys are the intermediate hosts but the muscle cysts are clinically silent. The final host has not been identified.

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